Acantholichen Marcano, 2022, s.str

Key to Acantholichen, Cyphellostereum and Dictyonema s.str. in Venezuela 1a. Thallus microsquamulose to microfruticulose, pruinose; squamules densely and dichotomously branched from the tips; photobiont forming clusters of short, irregularly coiled threads (chroococcoid) inside the thallus microsquamulose; soredia absent; upper and lower surfaces in microscope view forming apically thickened, distinctly spiny, pyriform to subglobose, variable in size, sometimes elongate hyphae (acanthohyphidia); clamp connections absent............................................. Acantholichen dendroideus 1b. Thallus composed of distinct fibrils including cyanobacterial filaments (Rhizonema); acanthohyphidia absent; clamp connections present or absent................................................................................................................................................................................2 2a. Thallus directly on bark of trunks or branches; lobes semicircular and/or hemispherical, variable in color, size and shape; basidiocarp N–; Venezuelan Andes or Guayana Highlands................................................................................................................................ (3) 2b. Thallus on mosses, liverworts or soil, appressed filamentous or loose and not forming semicircular lobes; basidiocarp N+ or N–; Venezuelan Andes (Sierra Nevada de Mérida)............................................................................................................................... (4) 3a (2). Thallus on tree branches; lobes projecting parallel from the substrate, semicircular and hemispherical, variable in color, size and shape; surface hirsute; clamp connections present; basidiocarp with resupinate patches dispersed on the underside and resembling large, irregular attachment, hapters, margin fibrillose; Venezuelan Andes (Sierra Nevada de Mérida)..... Dictyonema subsericeum 3b. Thallus on tree trunk, shelf–like filamentous, forming semicircular lobes, projecting upright from the substrate, surface areolate, rugose; clamp connections absent; basidiocarps forming irregular, reticulate, resupinate patches dispersed on the underside, margin entire; Guayana Highlands (Cerro Duida, Alto Orinoco).................................................................................. Dictyonema duidense 4a (2). Hymenophore resupinate; jigsaw-puzzle-shaped hyphal sheath present or absent; prothallus absent; clamp connections present or absent.............................................................................................................................................................................................. (5) 4b. Hymenophore corticioid; jigsaw-puzzle-shaped hyphal sheath present; prothallus present; clamp connections present.............. (6) 5a (4). Jigsaw-puzzle-shaped hyphal sheath absent; fibrils not penetrated by tubular fungal hyphae haustoria, horizontally arranged and closely appressed; cyanobacterial filaments 8–10 μm wide; clamp connections present; basidiocarp surface finely arachnoid, N–................................................................................................................................................................ Cyphellostereum mucuyense 5b. Jigsaw-puzzle-shaped hyphal sheath present; fibrils penetrated by tubular fungal hyphae haustoria, ascendent and loosely arranged; cyanobacterial filaments> 10 μm wide; clamp connections present or absent; basidiocarp surface smooth, N+ (pink)......................................................................................................................................................................................................... (7) 6a (4). Fibrils irregularly arranged, ascending or erect; cyanobacterial filaments not divided, 20–25 μm wide; hymenophores forming stereoid-corticioid patches, upper surface smooth, lower surface pruinose, spongy, N+ (red)......................... Dictyonema andinum 6b. Fibrils horizontal or subascending; cyanobacterial filaments divided, 13–17 μm wide hymenophores raised from the thallus, resembling apothecial discs, surface pale yellowish, smooth, margins white, minutely tomentose; N.......... Dictyonema umbricola 7a (5). Thallus developing a mat of interwoven fungal–cyanobacterial fibrils, leaving interspaces; cyanobacterial filaments 12–15 μm wide; clamp connections present; basidiocarp developed as effuse patches, with pruinose surface, margins slightly involute............................................................................................................................................................................. Dictyonema subinvolutum 7b. Thallus forming a thin crust (1.75–2 mm), bordered by a discontinuous, narrow, white margin projecting vertical from the substrate; cyanobacterial filaments 12–17 μm wide; clamp connections absent; basidiocarp hapteriform, with finely reticulate surface........................................................................................................................................................................................ Dictyonema laurae
Published as part of Marcano, Vicente, 2022, Eight new species of lichenized Basidiomycota in the genera Acantholichen, Cyphellostereum and Dictyonema s. str. (Agaricales, Hygrophoraceae) from northern South America, pp. 199-225 in Phytotaxa 574 (3) on page 220, DOI: 10.11646/phytotaxa.574.3.1, http://zenodo.org/record/7380966